This application claims the priority of German Application No. 100 09 075.3, filed Feb. 25, 2000, which is incorporated herein by reference.
The invention relates to a grinding attachment and a saw-blade grinding machine using the attachment, particularly for circular saw blades whose teeth have a hollow face.
Saw-blade grinding machines, which must be used in maintenance work for sharpening used saw blades, or in production, must be adaptable to the existing saw-blade conditions, or the tooth shape to be created. Usually, the tooth back and tooth face of a tooth of a saw blade, particularly in saw blades with hard-metal faces, must be ground. Tooth profiles may also be ground. The grinding shapes can vary. In some cases, it may be desirable to grind the tooth face to be hollow, while in other cases surface grinding is desired.
To produce a hollow grind on a tooth face, German published Patent Application No. DE 41 41 900 A1 discloses a hollow-face grinding method that operates with a cylindrical grinding body whose axis of rotation is oriented essentially parallel to the surface of the tooth face. The grinding body is a component of a grinding pencil or spindle that is brought into engagement with the tooth face in the center plane, or into two engaged positions that are offset relative to the center plane of the saw blade for grinding the tooth face. The direction of rotation is selected according to the direction of the offset.
Hollow-grinding the tooth face is necessary in some saw blades, but not all types. The saw-blade grinding machine is intended to be flexible in its use, without requiring retooling or modifications.
It is therefore the object of the invention to improve a saw-blade grinding machine to permit the machining of the widest-possible variety of saw blade types.
The above object generally is achieved according to the present invention by a grinding attachment for a grinding machine that comprises: a bearing support; a first shaft mounted on the bearing support for rotation about a first axis, with the first shaft being drive-connected to a driving device, and having at least one grinding wheel mounted on one end thereof; a second shaft mounted on the bearing support of the grinding attachment for rotation about a second axis, with the second shaft being drive-connected to the driving device for operation at a higher rpm than that of the first shaft and having at least one grinding tool mounted on one end thereof; and the second shaft is disposed in a region between the ends of the first shaft.
The above object generally is further achieved by a saw-blade grinding machine using the above described grinding attachment according to the invention.
The grinding attachment according to the invention has two shafts or spindles, which are connected to drives for different speeds or rpms. Whereas the first shaft or spindle can be provided at both ends with at least one grinding wheel, a grinding pencil or similar tool is disposed on the second shaft or spindle between the ends of the first shaft. The drives of the two shafts are preferably such that the ratio of the rpm or speed of the first shaft to the rpm or speed of the second shaft is similar to the ratio of the circumference of the grinding tool of the second shaft to the circumference of the (larger) grinding wheel of the first shaft. The grinding pencil of the second shaft runs at, for example, 10,000 to 60,000 rpm.
The arrangement of the second shaft in a region between the ends of the first shaft, i.e., preferably outside of a cylindrical or conical region enclosed by the two grinding wheels disposed at the two ends, results in a compact, stable design that only vibrates slightly, and yet permits good positioning. The high-speed grinding tool (e.g., a grinding pencil) can readily engage the tooth face of virtually any saw blade. The spacing of the grinding body of the grinding pencil from the axis of rotation of the first shaft is preferably at least as large as the radius of the larger grinding wheel, with the axes of rotation possibly intersecting or crossing one another. This prevents the grinding wheels from engaging the saw blade when the grinding pencil is supposed to be active. While the grinding wheels are operating, the grinding pencil is spaced from the saw blade. In this design, the positioning paths of the grinding attachments are short, permitting a fast, economical operation.
When the shafts provided on the grinding attachment are held in a fixed spatial arrangement, the resulting design is particularly compact and sturdy. The shafts provided on the grinding attachment are preferably seated on the bearing support such that they cannot be adjusted relative to one another.
The drives of the two shafts are preferably separate, and can therefore be actuated independently of one another. The driving device for the first shaft and the second shaft includes a first and a second drive, which drive the Respective shafts separately. The second drive is preferably a high-speed drive having an rpm (e.g., 60,000 rpm fixed) that is at least ten times higher than the rpm of the first shaft (e.g., 1000-6000 rpm). This permits the use of grinding tools having sharply differing diameters, for example, varying by more than one order of magnitude, on one and the same grinding attachment.
For positioning, it is advantageous for the first and second shafts to be perpendicular to one another, and to intersect one another or be offset from one another. The two shafts preferably extend in a plane that coincides with the center plane of the saw blade, or in a plane parallel to this plane.
In accordance with a further aspect of the invention, the saw-blade grinding machine has a machine stand on which all of the essential components of the saw-blade grinding machine, including the above described grinding attachment, are mounted. The machine stand holds a saw-blade carrier, which, in connection with a clamping apparatus, may be set up for fixedly supporting the saw blade in a machining position for the machining process. A device is also provided for advancing the saw blade tooth-by-tooth, thus transferring the teeth consecutively into the machining position. A separate advancing device, a so-called dividing finger, can be provided for this purpose. As an alternative, the advancing device can also be a component of the saw-blade carrier. It can engage the teeth of the saw blade or other locations of the saw blade, or the saw-blade carrier.
Preferably, an advancing device that can be variably controlled is used, so advancing increments can be set according to need. In a particularly preferred embodiment, the advancing increments are controlled individually for setting or varying the advancing increments on a saw blade.
At least one grinding attachment according to the invention, which has a bearing support, serves in machining the teeth. However, the grinding attachment can be divided and provided with first and second bearing supports, instead of a single bearing support. Each of the at least two shafts of the grinding attachment is provided with at least one dedicated grinding body. Whereas one shaft has one or more grinding wheels, the other has a grinding pencil. The first and second shafts are driven by a driving device, which is preferably divided into two separate drives that are actuated separately, preferably by a superordinate control device that also controls the rest of the grinding machine.
The grinding attachment is preferably embodied such that only one of the grinding bodies or tools engages the saw blade at a time. Accordingly, the drive of one shaft is adequate. The grinding pencil is provided for machining the tooth face. The grinding wheel(s) is (are) primarily provided for machining the tooth back and, if necessary, the tooth face.
Existing grinding attachments, or those correspondingly equipped in advance, can be retrofitted with the high-speed drive for the grinding pencil.
A positioning device supported by the machine stand permits two linear adjusting directions and, optionally, a pivoting movement about a pivoting axis extending perpendicular to the saw blade, and possibly a further pivoting axis. The pivoting permits an adaptation of the orientation of the grinding wheel and the grinding pencil to the tooth back and the tooth face. Additional linear axes permit an advancing movement. In an ideal case, three linear axes, oriented perpendicular to one another, are provided.
A significant advantage of the novel grinding machine is that saw blades whose teeth have a hollow face can be completely ground in one work cycle in a clamped arrangement with one machine. Manual intervention is typically not required, and the positioning paths are short.
The machine stand supports the positioning device for permitting a precise association and positioning relative to the saw blade. Instead of the above-mentioned pivoting axis extending perpendicular to the surface of the saw-blade, the saw blade can also be moved to a different position, in which instance the grinding attachment is not pivoted. This can be effected through an adjustment of the saw-blade carrier on a curved or straight path, to the side of a connecting line between the saw-blade carrier and the grinding attachment. Furthermore, the axis of rotation of the saw blade, in connection with the lateral adjustment of the grinding attachment, can replace the pivoting axis extending perpendicular to the saw-blade surface.
A control device controls the operation of the saw-blade grinding machines, controlling the positioning device and the advancing device, as well as the holding device and the driving device. Thus, the entire grinding process can be performed with control. The preferably flexible control device and the aforementioned arrangement of the other components allow complete machining of the saw blade in a clamped arrangement in one saw-blade grinding machine. The saw-blade grinding machine is also flexible and versatile.
For adaptation to different saw-blade diameters, the saw-blade carrier is preferably adjustably seated on the machine stand for setting the distance from the grinding attachment. As an alternative, the position of the grinding attachment can be adapted to various saw-blade diameters through an adjustment of the grinding attachment. In total, three linear axes are sufficient for setting the position. Moreover, at least one pivoting axis is present for the grinding attachment. If the saw-blade carrier is not fixedly, but rather adjustably, seated on the machine stand, the carrier preferably has an adjusting drive, which, like all of the other drives, is controlled by the control device. This permits a flexible machining of batches of different saw blades.
A clamping device, which is fixedly supported on the machine stand, is preferably provided in front of the grinding attachment as a holding device for supporting the saw blade, The clamping device grasps the saw blade in the vicinity of the tooth to be machined, and can preferably be controlled by the control device.
The grinding wheel disposed on the first shaft is provided, at least at its circumferential surface, with an abrasive material. In addition, its flat sides can be provided with an abrasive grain for machining different surfaces of the saw tooth.
The grinding pencil running with a high rpm and the highest rpm preferably has a cylindrical or conical grinding attachment. In an advantageous embodiment, its radius is larger than the thickness of a tooth of the saw blade when measured in the axial direction. To create a particularly deep, rounded, hollow cone on the tooth face, the diameter can be smaller than the tooth thickness.
Further details about advantageous embodiments of the invention are the subject of the dependent claims, the drawing and the description. The drawings illustrate an embodiment according to the invention.